Cummins/Onan DQCC troubleshooting: 57 fault codes and 14 symptom-cause-remedy entries from the manufacturer's own service documentation.
Cummins/Onan DQCC — full specs, parts & maintenance.
All Cummins/Onan fault codes →
| Code | Meaning | Remedy |
|---|---|---|
| 59 | High AC voltage shutdown | Output voltage on any phase exceeds preset values. Time to trip is inversely proportional to amount above threshold. Values adjustable from 105-125% of nominal voltage, with time delay adjustable from 0.1-10 seconds. Default value is 110% for 10 seconds. |
| 27 | Low AC voltage shutdown | Voltage on any phase has dropped below a preset value. Adjustable over a range of 50-95% of reference voltage, time delay 2-20 seconds. Default value is 85% for 10 seconds. Function tracks reference voltage. Control does not nuisance trip when voltage varies due to the control directing voltage to drop, such as during a V/Hz roll-off during synchronizing. |
| 81 u | Under frequency shutdown | Generator set output frequency cannot be maintained. Settings are adjustable from 2-10 Hz below reference governor set point, for a 5-20 second time delay. Default: 6 Hz, 10 seconds. Over frequency shutdown/warning is disabled when excitation is switched off, such as when engine is operating in idle speed mode. |
| 81 o | Over frequency shutdown/warning | Generator set is operating at a potentially damaging frequency level. Settings are adjustable from 2-10 Hz above nominal governor set point for a 1-20 second time delay. Default: 6 Hz, 20 seconds, disabled. |
| 121 | Speed Signal Lost | |
| 135 | Oil Pressure Sensor High | |
| 141 | Oil Pressure Sensor Low | |
| 143 | Pre-Low Oil Pressure Sensor | |
| 144 | Coolant Temperature Sensor High | |
| 145 | Coolant Temperature Sensor Low | |
| 146 | Pre-High Cool Temp | |
| 151 | High Coolant Temp | |
| 197 | Low Coolant Level | |
| 234 | Overspeed | |
| 235 | Low Coolant Level | |
| 359 | Fail to Start | |
| 415 | Low Oil Pressure | |
| 441 | Low Battery Voltage | |
| 442 | High Battery Voltage | |
| 1123 | Shutdown After Battle Short | |
| 1124 | Delayed Shutdown | |
| 1131 | Battle Short Active | |
| 1244 | Engine Normal Shutdown | |
| 1311 | Customer Inputs #1 | |
| 1312 | Customer Inputs #2 | |
| 1317 | Customer Inputs #3 | |
| 1318 | Customer Inputs #4 | |
| 1334 | Crit Scaler OR | |
| 1335 | Non-Crit Scaler OR | |
| 1416 | Fail to Shutdown | |
| 1417 | Power Down Failure | |
| 1433 | Emergency Stop | |
| 1434 | Remote Emergency Stop | |
| 1435 | Low Coolant Temperature | |
| 1438 | Fail to Crank | |
| 1442 | Weak Battery | |
| 1443 | Battery Failed | |
| 1444 | KW Overload | |
| 1445 | Short Circuit | |
| 1446 | High AC Voltage | |
| 1447 | Low AC Voltage | |
| 1448 | Under Frequency | |
| 1449 | Over Frequency | |
| 1461 | Loss of Field | |
| 1466 | Modem Failure | |
| 1468 | Network Error | |
| 1469 | Speed/Hz Match | |
| 1471 | Over Current | |
| 1472 | Over Current | |
| 2335 | Excitation Fault | |
| 2336 | Memory Error | |
| 2341 | High Control Temperature | |
| 2342 | Too Long in Idle | |
| 2967 | Governor Fault | |
| 2968 | AVR Fault | |
| 2969 | LON Failure | |
| 2972 | Field Overload |
| Symptom | Remedy |
|---|---|
| Battle Short Mode | If a bypassed shutdown fault occurs, the fault code and description will still be annunciated, but the genset will not shutdown. This will be followed by a fail to shutdown fault. |
| Derate | The derate function reduces output power of the genset in response to a fault condition. If a derate command occurs while operating on an isolated bus, the control will issue commands to reduce the load on the genset via contact closures or modbus. |
| Emergency Stop | Annunciated whenever either emergency stop signal is received from external switch. |
| Full Authority Electronic Engine Protection | Engine fault detection is handled inside the engine ECM. Fault information is communicated via the SAE-J1939 data link for annunciation in the HMI. |
| Low and high battery voltage warning | Indicates status of battery charging system (failure) by continuously monitoring battery voltage. |
| Weak battery warning | The control system will test the battery each time the generator set is signaled to start and indicate a warning if the battery indicates impending failure. |
| Fail to start (overcrank) shutdown | The control system will indicate a fault if the generator set fails to start by the completion of the engine crack sequence. |
| Fail to crank shutdown | Control has signaled starter to crank engine but engine does not rotate. |
| Cranking lockout | The control will not allow the starter to attempt to engage or to crank the engine when the engine is rotating. |
| Overcurrent warning/shutdown | Thresholds and time delays are configurable. Implementation of the thermal damage curve with instantaneous trip level calculated based on current transformer ratio and application power rating. |
| Loss of sensing voltage shutdown | Shutdown of generator set will occur on loss of voltage sensing inputs to the control. |
| Field overload shutdown | Monitors field voltage to shutdown generator set when a field overload condition occurs. |
| Over load (kW) warning | Provides a warning indication when engine is operating at a load level over a set point. Adjustment range: 80-140% of application rated kW, 0-120 second delay. Defaults: 105%, 60 seconds. |
| Reverse power shutdown | Adjustment range: 5 |
Fault codes and symptom→remedy steps extracted from this model’s service/owner documentation; verify against the official manual before servicing.